Been feeding my hens everything from leftover lasagne to old hamberger(cooked, but not spoiled, just too old to eat) for years, and of course anything that I would throw in the compost pile.( My compost pile is non-excistant now though)
My eggs are the tastiest eggs, and everyone who buys them can't wait to get more! I also feed them dog food in the can, or dog kibble at times(mainly in the winter) when I run out of layer hen crumbles. I live in southern Oregon, we have very cold, snowy winters, and my chicken have never been sick. I have given them some antibiotic a couple of times in their water to make sure that they didn't have a upper respiritory when I got some new chicks. I introduced 20 new chicks a month ago, and so didn't want the old hens (4 years) to have something that they could have given the chicks.
I think one reason my chickens are so healthy is because we have 2 of the heartiest breeds Barred Rock, and Roade Island Reds. I am weeding out the Reds, as they are too aggressive. They pick at the Barred Rocks feathers. I love my Barred Rock chicks, they are my pets, where the Reds are skiddish, and jumpy, and mean. I have 3 reds left, and when my chicks start layeing they are going to be dog food! The Barred Rock chickens are a tough breed, they go out in the snow in the winter, and love it! I think getting a tough breed verses a "cute" chicken is paramount to having a healthy flock!